Valve locking device

ABSTRACT

A valve locking device comprising an intermediate member (18) mountable between a valve body and valve actuator and securable to said valve body and/or actuator; a stem attachment member (20) attachable to and rotatable with a valve stem (14) and contained at least partially within said intermediate member, and an engagement member (22) movably located within said intermediate member for selective engagement with said stem attachment member; whereby in use, engagement between said engagement member and said stem attachment member prevents rotation of said stem attachment member, thus preventing rotation of said valve stem to operate the valve.

FIELD OF THE INVENTION

[0001] The present invention relates to valve locking devices forlocking a valve in a particular position to prevent it moving from anopen position to a closed position or vice versa. In particular, thepresent invention relates to a valve locking device which is mountablebetween a valve and valve actuator.

BACKGROUND TO THE INVENTION

[0002] In many industrial installations valves are used in circumstanceswhere their incorrect operation could lead to accidents resulting inserious damage or injury. For example, many factories utilise pressurevessels which need to be entered by workers for maintenance and/orrepair. It is essential that valves controlling supply of fluid underpressure to such vessels are locked in the shut or closed position whensuch maintenance or repair is taking place. In other situations it maybe important for safety purposes that a valve is not closed. Forexample, dosing a valve may prevent adequate ventilation.

[0003] Typically butterfly valves, ball valves and plug valves are usedunder the circumstances referred to. Butterfly valves, ball valves andplug valves typically require only a quarter turn of an operatingspindle between closed and open positions. However, some ball valvesrequire rotation of an operating spindle through 180 degrees betweenclosed and open positions. A valve actuator is typically used to rotatean operating spindle.

[0004] Past attempts to address the abovementioned safety issues haveinvolved placing a hood over the valve actuator. However, the hoods aretypically cumbersome to use and not always effective.

[0005] The inventor of the present invention developed the valve lockingdevice which is described in South African Patent No. 97/10910 for thepurpose of addressing the abovementioned safety issues. The valvelocking device of South African Patent No. 97/10910 generally comprisesa rigid metal u-shaped frame which has a cross plate that is welded toextend across the mouth of the u-shaped frame. The u-shaped frame isdesigned to slidably receive a spindle engaging plate that has a slotformed in one of its ends.

[0006] The u-shaped frame is designed to mount between a valve and itscorresponding valve actuator in the process of assembling the valve andvalve actuator. The slot of the spindle engaging plate is designed sothat it receives a square sectioned spindle of the valve, which extendsbetween the valve and valve actuator. when the spindle engaging plate isappropriately received in the u-shaped frame, Rotation of the spindle isprevented when the spindle is positioned within the slot of the spindlereceiving plate. The cross plate and spindle engaging plate havecorresponding holes to enable the spindle engaging plate to be fixedrelative to the cross plates, ensuring that the spindle ngaging plateremains fixed relative to the u-shaped frame.

[0007] While the valve locking device of 97/10910 addresses theabovementioned safety issues, the inventor estimates that it may beprone to failure after 100 cycles at approximately 50% torque.

[0008] It is therefore desirable to provide an improved valve lockingdevice.

SUMMARY OF THE INVENTION

[0009] In the first aspect, the present invention provides a valvelocking device comprising:

[0010] an intermediate member mountable between a valve body and valveactuator and securable to said valve body and/or valve actuator;

[0011] a stem attachment member attachable to and rotatable with a valvestem, and contained at least partially within said intermediate member;and

[0012] an engagement member movably located within said intermediatemember for selective engagement with said stem. attachment member;

[0013] whereby in use, engagement between said engagement member andsaid stem attachment member prevents rotation of said stem attachmentmember, thereby preventing rotation of said valve stem to operate thevalve.

[0014] Suitably said engagement member is slidably movable in saidintermediate member.

[0015] If required, said stem attachment member may b adapted to extendinto a recess in said valve body to increase surface engagement betweensaid valve stem and said stem attachment member.

[0016] Suitably said engagement member may be locked in an engagedposition or a disengaged position.

[0017] The device may include a locking means for locking saidengagement member in an engaged position or a disengaged position.

[0018] If required the stem attachment member may be adapted forengagement with said engagement member in two or more rotationallyspaced positions.

[0019] In a second aspect, the present invention provides a combinationof a valve locking device of the first aspect of the present invention,a valve, and valve actuator, wherein operation of the valve by the valveactuator is preventable by said valve locking device.

[0020] The valve actuator of the second aspect of the present inventionmay be a powered mechanism.

[0021] Alternatively, the valve actuator of the second aspect of thepresent invention may be manually operated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A preferred embodiment of the present invention will now bedescribed by way of example only, with reference to the accompanyingdrawings in which:

[0023]FIG. 1 is an isometric view of a butterfly valve, and a valve lockwherein the components of the valve lock are unassembled;

[0024]FIG. 2 is an isometric view of the butterfly valve and valve lockof FIG. 1, as assembled, with the valve lock in an unlocked position;

[0025]FIG. 3 is an isometric view similar to FIG. 2 with the valve lockin a locked position;

[0026]FIGS. 4a and 4 b are isometric views of alternative spindlereceiving discs of the valve lock of FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0027] Referring to FIG. 1, a butterfly valve 12 having an end 10, fromwhich a spindle 14 extends, is typically bolted to a valve actuator (notshown). The valve actuator functions to rotate the spindle 14 of thebutterfly valve 12. Rotation of the spindle 14 results in movement of avalve 16 of the butterfly valve 12 between open and closed positions.

[0028] The unassembled valve lock of FIG. 1, which provides an exampleof the valve locking device, comprises a plate 18, a cylindricallyshaped spindle receiving disc 20 and a key 22. The plate 18, spindlereceiving disc 20 and key 22 provide an example of the intermediatemember, spindle attachment member and engagement member respectively.One end 24 of the plate 18 is generally square in shape while the otherend 26 of the plate 18 is generally rectangular In shape. However, Itwill be appreciated by a person skilled in the relevant field thatdepending on the shape of a valve and/or valve actuator, a plate couldbe shaped differently to the plate 18 to enable it to be mounted betweenthe valve and valve actuator. and secured to either or both the valveand valve actuator. The rectangular shaped end 26 is positionedcentrally relative to the square end 24. Four holes 28 are formed incorner regions of the square end 24 for mounting of the plate 18 betweenthe butterfly valve 12 and valve actuator. However as explained above,the position, number and spacing of holes formed in a plate which ismounted between a valve and valve actuator may vary in accordance withengineering design practice, dependent on the particular valve and valveactuator.

[0029] Material is removed from both the square and rectangular shapedends 24 and 26 to allow for receipt of the spindle receiving disc 20 andkey 22 respectively. A hole 30 is formed in the square shaped end 24 sothat an axis of the hole 30 extends transversely relative to the plate18 and is approximately centrally positioned within the square shapedend 24. A slot 32 is formed in the rectangular shaped end 26. The slot32 is one example of the guide means. The slot 32 is positionedapproximately centrally across the width of the rectangular shaped end26 and extends from one end of the rectangular shaped end 26 beyond theother end of the rectangular shaped end 26 and into the square shapedend 24 so that the slot 32 intersects the hole 30. The hole 30 and slot32 extend through the thickness of plate 18.

[0030] The diameter of the spindle receiving disc 20 is such that it canfit into the hole 30. A square shaped slot 34 is formed in the spindlereceiving disc 20. The square shaped slot 34 extends through thethickness of the spindle receiving disc 20. A distance of approximately17 mm separates the longitudinal axis of the spindle receiving disc andthe square shaped slot 34.

[0031] A square shaped hole 36 which extends through the thickness ofthe spindle receiving disc 20 is positioned centrally off the spindlereceiving disc 34. Each wall which forms the square shaped hole 36 isapproximately 19 mm in length. Two of the walls which form the squareshaped hole 36 are parallel to and aligned with two opposite walls whichform the square shaped slot 34. The square shaped hole 36 is suitablydimensioned to receive the square sectioned spindle 14 of the butterflyvalve 12.

[0032] The key 22 includes a rectangular bar 38 which is suitablydimensioned for receipt in the square shaped slot 32 of the plate 18.The key 22 also includes a rectangular sectioned cross member bar 40which extends transversely of the rectangular sectioned bar 38. Therectangular sectioned cross member bar 40 is position d at one nd of therectangular sectioned bar 38 so that a longitudinal wall 42 of therectangular sectioned cross member bar 40 is flush with an end of therectangular sectioned bar 38. The rectangular sectioned bar 38 andrectangular sectioned cross member bar 40 are orientated relative toeach other so that each of them contact the other via wider rather thannarrower walls. The rectangular sectioned bar 38 and rectangularsectioned cross member bar 40 are welded and also bolted together.

[0033] The plate 18, spindle receiving disc 20 and key 22 are assembledbetween the butterfly valve 12 and valve actuator as follows. The plate18 is positioned against an end 10 of the butterfly valve 12 by passingbolts through holes 28 of the plate 18. With the plate 18 positioned inthis way the spindle 14 of the butterfly valve 12 extends approximatelycentrally through the hole 30 of the plate 18.

[0034] Referring to FIG. 2, the spindle receiving disc 20 is positionedrelative to the spindle 14 so that the spindle 14 passes through thesquare shaped hole 36 formed in the spindle receiving disc 20, and sothat the spindle receiving disc 20 is received within the hole 30 thatis formed in the plate 18. The key 22 is orientated relative to theplate 18 so that the rectangular sectioned bar 38 is received within theslot 32, and so that the rectangular sectioned cross member bar 40 ispositioned away from the spindle receiving disc 20. By positioning thekey 22 in this way the rectangular sectioned cross member bar 40contacts a surface of th plate 18 which is opposite the surface of theplate 18 that contacts an end 10 of the butterfly valve 12.

[0035] The cylindrically shaped spindle receiving disc 20 fits into arecess 44 (see FIG. 1) which is formed in the end 10 of the butterflyvalve 12. The diameter of the recess 44 is slightly larger than thediameter of the spindle receiving disc 20, and the spindle 14 ispositioned centrally relative to the recess 44. The spindle receivingdisc 20 can therefore be fitted into the recess 44. The thickness of thespindle receiving disc 20 is greater than the thickness of the plate 18.The increased thickness of the spindle receiving disc 20 compared withthe thickness of the plate 18 increases the capability of the spindlereceiving disc 20 to withstand loads which are applied by the spindle 14when the key 22 is received within the square shaped slot 34.

[0036] While the recess 44 is formed in the end 10 of the butterflyvalve 12, some valves may not have a recess corresponding to the recess44. in such cases, the thickness of the spindle receiving disc 20 willbe limited to the thickness of the plate 18. In some cases the length ofthe spindle 14 will be such that the thickness of the plate whichreceives the spindle receiving disc can be increased to enable thethickness of the spindle receiving disc to be equivalent to thethickness of the spindle receiving disc 20. However, in other cases, thelength of the spindle 14 will be such that the thickness of the spindlereceiving disc must be less than the thickness of the spindle receivingdisc 20. Depending on the particular valve and application, it may bedesirable to produce the spindle receiving disc 20 from materials whichenable the spindle receiving disc to withstand loads applied by acorresponding spindle which the spindle receiving disc 20 is capable ofwithstanding.

[0037] With the plate 18 fitted against the end 10 of the butterflyvalve 12, and the spindle receiving disc 20 and key 22 appropriatelyassembled in the plate 18, the valve actuator (not shown) can beappropriately bolted to the butterfly valve 12 to clamp the assembledvalve lock 46 (see FIGS. 2 and 3) between the butterfly valve 12 and thevalve actuator. With the assembled valve lock 46 clamped between thebutterfly valve 12 and the valve actuator, the rectangular sectionedcross member bar 40 can be moved toward and away from the spindle 14 tomove the valve lock 46 between locked and unlocked positionsrespectively, as long as the slot 34 of the spindle receiving disc 20 isappropriately positioned to receive an end of the rectangular sectionedbar 38. An exposed bolt head 47 and corresponding nut 48 make grippingand subsequent moving of the key 22 between locked and unlockedpositions easier.

[0038] Appropriate orientation of the spindle receiving disc 20 relativeto the square sectioned spindle 14 prior to insertion of the spindle 14through the square shaped hole 36 is required to ensure correct and safeoperation of the assembled valve lock 46. The spindle receiving disc 20can be orientated so that the square shaped slot 34 of the spindlereceiving disc 20 is positioned at four different positions about alongitudinal axis of the spindle 14. Each of the four positions areither 90 degrees or 180 degrees out of phase relative to each of theother positions. The correct orientation of the square shaped slot 34relative to the spindle 14 is therefore required prior to assembly ofthe assembled valve lock 46. To ensure correct orientation, the positionof the valve 16 of the butterfly valve 12 must be taken intoconsideration when inserting the spindle 14 through the square shapedhole 36 of the spindle receiving disc 20. One method of ensuringappropriate orientation of the spindle receiving disc 20 prior toassembly is to place the valve 16 of the butterfly valve 12 in aposition which the valve 16 is required to be locked in by the assembledvalve lock 46 prior to assembly of the assembled valve lock 46. With thevalve 16 positioned in this manner, the spindle receiving disc 20 can beorientated relative to the spindle 14 so that assembly of the assembledvalve lock 46 results in the square shaped slot 34 being suitablypositioned for receipt of the rectangular sectioned bar 38 of the key22. After assembly of the assembled valve lock 46 the key 22 can bemoved to the locked position to check that the rectangular sectioned bar38 is able to be received within the square shaped slot 34 when thevalve 16 is in a position which is required to be locked by theassembled valve lock 46. The position in which the valve 16 of thebutterfly valve 12 is required to be locked in could be either a fullyopen or fully closed position. The locking position can be adjusted bydisassembling the assembled valve lock 46 and appropriately orientatingthe spindl receiving disc 20 prior to reassembling th assembled valvelock 46.

[0039] Some ball valves require a 180 degree rotation of an operatingspindle between closed and open positions. By appropriately orientatingspindle receiving disc 20 prior to assembly of an assembled valve locksuch as the valve lock 46, the spindle receiving disc 20 which has asingle square shaped slot 34 can be used to lock such a ball valve inany one of the following positions: fully open; partially open; andclosed.

[0040] Referring to FIGS. 1-3, corresponding holes 49 and 50 areprovided in opposite ends of the rectangular sectioned cross member bar40, and the plate 18, either side of the rectangular slot 32. The holes49 and 50 enable the key 22 to be fixed in either the locked position orunlocked position by passage of bolts therethrough.

[0041] In some situations it may be important that a valve is able to belocked in more than one position. Alternative spindle receiving discs52, 54, and 56 of FIGS. 4a, 4 b, and 4 c respectively are examples ofspindle receiving discs that can be used in these situations. Thealternative spindle receiving disc 52 has two square shaped slots 34which are identical to the square shaped slot 34 of FIGS. 1-3. Thesquare shaped slots 52 of FIG. 4a are positioned so that they extend at90 degrees relative to each other. By replacing the spindle receivingdisc 20 of the assembled valve lock 46 with the alternative spindlereceiving disc 52, the assembled valve lock 46 can be used to lock thevalve 16 of the butterfly valve 12 in opposite positions. For example,the alternative spindle receiving disc 52 can be used to lock thebutterfly valve 12 in fully open and fully closed positions.

[0042] The alternative spindle receiving disc 54 has two square shapedslots 34 which are identical to the square shaped slots 34 of FIG. 4a.

[0043] However, the spindle receiving disc 54 of FIG. 4b differs fromthe spindle receiving disc 52 of FIG. 4a in that the square shaped slots34 are positioned opposite each other. The alternative spindle receivingdisc 54 can be used in place of the spindle receiving disc 20 to form anassembled valve lock 46 which is capable of locking a specific type ofbail valve, which requires a 180 degree rotation of an operating spindlebetween open and closed positions, in fully open and fully closedpositions.

[0044] The alternative spindle receiving disc 56 of FIG. 4c has foursquare shaped slots 34 which are identical to the square shaped slots 34of FIGS. 4a and 4 b, and a fifth rectangular shaped slot 58. The squareshaped slots 34 are equidistantly spaced from each other around thespindle receiving disc 56 so that each square shaped slot 34 extends atan angle of 90 degrees relative to adjacent square shaped slots 34. Therectangular shaped slot 58 is positioned between two adjacent squareshaped slots 34 and is equally distantly spaced from each adjacent slot34. The rectangular shaped slot 58 extends through the thickness of thespindle receiving disc 56 as do the square shaped slots 34. While therectangular shaped slot 58 is as wide as the square shaped slots 34, itis approximately half the depth of the square shaped slots 34. Byreducing the depth of the rectangular shaped slots 58 relative to thedepth of the square shaped slots 34, the effect of the rectangularshaped slot 58 on the structural integrity of the spindle receiving disc56 is decreased. The spindle receiving disc 56 can be used to lock abutterfly valve in fully open and fully closed positions by engagementbetween a member such as the rectangular sectioned bar 38 of the key 22and one of the square shaped slots 34 of the spindle receiving disc 56.The spindle receiving disc 56 can be used to lock a butterfly valve inthe fully open and fully closed positions, regardless of how the spindlereceiving disc 56 was orientated prior to insertion of the squaresectioned spindle 14 of the butterfly valve 12 into the square shapedhole 36 of the spindle receiving disc 56. The rectangular shaped slot 58enables the valve 16 of the butterfly valve 12 to be locked in apartially opened position by engagement between the rectangularsectioned bar 38 of the key 22, and the rectangular sectioned slot 58.The spindle receiving disc 56 is required to be appropriately orientatedprior to insertion of the spindle 14 through the square shaped hole 36to enable the rectangular shaped slot 58 to be engaged by therectangular sectioned bar 38.

[0045] While the spindle receiving discs 52, 54 and 56 enable a valve tobe locked in more than one position, for example, fully open and fullyclosed positions, in the case of spindle receiving discs 52 and 54, andfully open, fully closed and partially open positions in the case of thespindle receiving disc 56, there are possible safety relateddisadvantages associated with spindle receiving discs 52, 54 and 56 thatdo not ads with use of spindle receiving discs such as spindl receivingdisc 20 which provide a single locked position. The potential safetyissu s associated with spindle receiving disc 52, 54 and 56 arisebecause a valve can be locked in more than one position. If the spindlereceiving disc 20 is appropriately orientated relative to the spindle14, prior to insertion of the square sectioned spindle 14 into thesquare shaped hole 36 of the spindle receiving disc 20, engagementbetween the rectangular sectioned bar 38 and square shaped slots 34ensures that the valve 16 of the butterfly valve 12 is locked in therequired position. As such, simple inspection of whether or not the key22 is in the locked position ensures that the valve 16 is in a positionwhich will not endanger workers working in the vicinity of the butterflyvalve 12. However, in the case of the alternative spindle receivingdiscs 52, 54 or 56, engagement between the rectangular sectioned bar 38and square shaped slot 34 means that a valve which is associated with avalve locking incorporating alternative spindle receiving discs 52, 54or 56 could be in either a fully open or closed position. In cases wherethe alternative spindle receiving disc 54 is used with ball valves thatrequire rotation of an operating spindle through 180 degrees betweenopen and closed positions, engagement between the rectangular sectionedbar 38 and square shaped slot 34 could also mean that an associatedvalve is in a partially open position. Engagement between therectangular slot 58 of the alternative spindle receiving disc 56indicates that an associated valve is in a partially open position. Theposition of a valve (ie. whether it is in an open, closed or partiallyopen position) associated with valve locks incorporating spindlereceiving discs 52. 54 or 56 is therefore not ascertainable by visualinspection of whether the key 22 is in a locked position. Engagementbetween the rectangular sectioned bar 38 and rectangular shaped slot 58of the spindle receiving disc 56 would result in the key 22 being in aslightly different position to the locked position corresponding toengagement of the key 22 with the square shaped slots 34. However, thelocked positions corresponding to engagement with the rectangular shapedslot 58, and square shaped slots 34 could be easily confused.

[0046] It follows that additional safety procedures should beimplemented with use of spindle receiving discs such as spindlereceiving discs 52, 54 and 56 to ensure that associated valves arelocked in a position which ensures safety of workers working in thevicinity of the associated valves. Such additional safety procedurescould for example include the use of flow meters or proximity switches.They could also include additional visual inspection procedures. Theadditional visual inspection procedures could for example, in the caseof a tank outlet, include visual inspection of the outlet to confirmwhether an associated valve is in an open or closed position.

[0047] Although the spindle 14 of the butterfly valve 12 is a squaresectioned spindle, the section of the spindle can be varied as long asthe spindle receiving discs 20, 52 and 54 are correspondingly varied toenable engagement between the spindle receiving discs 20, 52 and 54, andthe spindle 14. For example, the cross sectional shape of the spindle 14could be hexagonal. The cross sectional shape could also corr spond tothe shape formed by two oppositely positioned flats which extend alongpart of the longitudinal length of a cylindrically shaped spindle. Asplined engagement system could also be used for providing engagementbetween the spindle receiving discs 20, 52 and 54, and the spindle 14.

[0048] Although the rectangular sectioned cross member bar 40 can besecured in the locked and unlocked positions by passage of bolts throughaligned holes 49 and 50, in order to minimise the risk of the assembledvalve lock 46 being moved from a locked position when it is importantfor the valve lock to be maintained in such a position, a safety padlock(not shown) is preferably used to fix the rectangular sectioned crossmember bar 40 in the locked position.

[0049] The safety padlock includes two arms which are pivotally attachedto each other. The end of the pivotally attached arms which are distalthe pivot point are designed to overlap when the safety padlock isclosed. Corresponding holes are formed in overlapping ends of thepivotally attached arms with each of the corresponding holes beingsuitable for insertion of a shackle of a padlock. A typical safetypadlock includes five corresponding holes and is therefore capable ofreceiving up to five padlocks. Unless all of the padlocks are removedfrom corresponding holes of the safety padlock, the safety padlockcannot be removed from corresponding holes 49 and 50 of the assembledvalve lock 46.

[0050] Employees whose safety is dependent upon whether a particularvalve is in an open or closed positlon, can be assigned separatepadlocks for us with the safety padlock. If a work r is to perform atask which requires a valve to be in either an open or closed position,prior to performing the task they can appropriately fix the assembledvalve locking device 46 in an appropriately locked position by attachingtheir padlock to the safety padlock. In using this system it isobviously important that the different workers whose safety is dependenton the appropriate operation of a particular valve are issued withuniquely keyed padlocks. In situations where more than five workers mayneed to secure the assembled valve lock 46 in a locked position, safetypadlocks which are capable of receiving more than five padlocks shouldbe designed for this purpose.

[0051] As an alternative to the use of the safety padlock, separatepadlocks may be used to secure a key 22 in the locked and unlockedpositions by passage of a shackle of each padlock through separatecorresponding holes of the key 22 and plate 18. Such a method would workwell for example if there are only two workers whose safety is at riskby the appropriate operation of a valve. In this situation, the workerscould have uniquely keyed padlocks which at all times could be used tosecure the assembled valve lock 46 in either a locked or unlockedposition. In cases where the safety of more than two workers, forexample four workers, is dependent upon the appropriate operation of avalve, the rectangular sectioned cross member bar 40 and plate 18 couldbe altered as follows. The length of the rectangular sectioned crossmember bar 40 could be extended, and the dimensions of the plate 18could als b appropriate altered, to enable two additional holes similarto holes 49 to be formed in the rectangular sectioned cross member bar40, and additional holes similar to holes 50 to be formed in the plate18 to enable the key 22 to be secured in locked and unlocked positionsby four separate padlocks. As in the case of the previous examples, byutilising four uniquely keyed padlocks, the four workers can ensure thatat any given time the key 22 is secured in a locked or unlockedposition, in accordance with their safety requirements.

[0052] As explained above, the assembled valve locking device 46 ofFIGS. 2 and 3 is designed to lock the valve 16 in one or more specificpositions by engagement between the rectangular sectioned bars 38 andthe spindle receiving disc 20. The particular form of engagementdescribed above involves receipt of the rectangular sectioned bar 38into a rectangular shaped slot 34 of the spindle receiving disc 20.However, the present invention is not limited to the specific form ofengagement shown in FIGS. 14. For example, engagement could be providedby insertion of a rod or bar into a hole appropriately formed into thespindle receiving disc 20. The present invention is also not limited tothe specific mechanism of FIGS. 1-3 by which engagement is effected.

[0053] For example, the key 22 could be designed to engage two or moreflat surfaces which are formed in an external circumferential surface ofthe spindle receiving disc 20, and positioned opposite each other. Toenable this form of engagement the rectangular sectioned bar 38 wouldneed to be wide enough to enable a slot to be formed in one of its endsthat is suitable for engaging with the aforementioned flat surfaces ofthe spindle receiving disc 20. Additional material would need to beremoved from the plate 18 for receipt of the alternative key 22, and toenable the alternative key 22 to move between locked and unlockedpositions.

[0054] Regarding the mechanism by which the engagement is effected, themechanism could for example involve pivotal movement of an alternativerectangular sectioned bar (not shown) which provides a functioncorresponding to the function of the rectangular sectioned bar 38. Thealternative rectangular sectioned bar could be pivotally attached via afirst end so that a second end moves into and out of the slot 32 withpivotal movement of the alternative rectangular sectioned bar. With therectangular shaped slot 34 appropriately orientated relative to thealternative rectangular sectioned bar pivotal movement of thealternative rectangular sectioned bar into the slot 32 would result inreceipt of the second end of the rectangular sectioned bar within therectangular shaped slot 34. Movement of the alternative rectangularsectioned bar out of the slot 32 would require the alternative sectionedbar moving toward the actuator. The actuator would therefore need to bedesigned with this movement in mind so that movement of the alternativerectangular sectioned bar to a positioning which does not engage therectangular shaped slot 34 would not be prevented by the actuatorhousing.

The claims defining the invention are as follows:
 1. A valve lockingdevice comprising: an intermediate member mountable between a valve bodyand valve actuator and securable to said valve body and/or valveactuator; a stem attachment member attachable to and rotatable with avalve stem, and contained at least partially within said intermediatemember; and an engagement member movably located within saidintermediate member for selective engagement with said stem attachmentmember; whereby in use, engagement between said engagement member andsaid stem attachment member prevents rotation of said stem attachmentmember, thereby preventing rotation of said valve stem to operate thevalve.
 2. A valve locking device as claimed in claim 1 wherein saidengagement member is slidably moveable in said intermediate member.
 3. Avalve lock as claimed in claim 1 or claim 2 wherein the stem attachmentmember is adapted to extend into a recess in said valve body to increasethe surface engagement between said valve stem and said stem attachmentmember.